Wood is a common material used to construct doors and other architectural building elements. Even today, after the development of several new species of composite materials, wood remains one of the most widely-used structural materials because of its excellent strength and stiffness, pleasing aesthetics, good insulation properties and easy workability.
However, in recent years the cost of solid timber wood has increased dramatically as its supply shrinks due to the gradual depletion of old-growth and virgin forests. It is particularly expensive to manufacture doors from such material because typically less than half of harvested timber wood is converted to natural solid wood lumber, the remainder being discarded as scrap.
Accordingly, because of both the cost of high-grade timber wood as well as a heightened emphasis on conserving natural resources, wood-based alternatives to natural solid wood lumber have been developed that make more efficient use of harvested wood and reduce the amount of wood discarded as scrap. Plywood, particle board and oriented strand board (“OSB”) are examples of wood-based composite alternatives to natural solid wood lumber that have replaced natural solid wood lumber in many structural applications in the last seventy-five years. These wood-based composites not only use the available supply of timber wood more efficiently, but they can also be formed from lower-grade wood species, and even from wood wastes.
However, decreasing wood supplies and lower wood quality are putting increasing stress on the quality of and raw material prices for OSB. Wood species often must be mixed in the process in order to have enough wood to make continuing supply of composite panels. If these species are of differing densities, there are problems with the mixing of them in the panel. For example, if a clump of one species or the other were to form in the panel due to inadequate mixing in the process, then the area of the clumped species would have a density that is either higher or lower than the overall average density of the panel. This could cause visual and structural problems with the panel since lower density clumped material may form a weak spot and high density clumped material may cause a stronger and harder area which may be harder to sand. Given the foregoing, there is a continuing need for a wood composite material that can address these inadequacies. Notably this wood composite material would have superior or comparable performance to solid wood lumber while being lighter (lower density) than conventional mixed-species OSB materials, have a more uniform appearance and more consistent physical properties. Additionally, this wood composite material would incorporate to some extent fibers harvested from lignocellulosic species that are faster growing than those species which are conventionally used for wood composite materials.
Examples of such faster growing lignocellulosic species include tree species from the genus Paulownia, as well as trees grown on managed (irrigation and fertilization) plantations. Examples of non-tree lignocellulosic materials include annual and perennial grasses such as wheat straw and the various species of bamboo. These can be grown and harvested very quickly after planting, and can give a more frequent harvest schedule than that of typical tree species. Additionally, these species would be mixed into a wood composite material in such a way that the strengths of the materials would be emphasized while the weaknesses of the materials would be minimized for the final product. Mixing a small amount of a superior material into a wood composite in this manner would serve to maximize the value of the superior material while at the same time conserving it, especially if the material was in short supply or was expensive to procure.